Transmitting characteristic for multiaperture cores



Jan. 3, 1967 w. B. FRITZ 3,296,601

TRANSMITTING CHARACTERISTIC FOR MULTIAPERTURE CORES Filed April 6. 1962HIMIIIIMIII! l T T i PRH E.

INVENTOR. Wuuam B. FRrTz M Wfl-W United States Patent 3,296,601TRANSMITTING CHARACTERISTIC FOR MULTIAPERTURE CORES William B. Fritz,Linglestown, Pa., assignor to AMP Incorporated, Harrisburg, Pa.

Filed Apr. 6, 1962, Ser. No. 185,727 8 Claims. (Cl. 340174) The presentinvention relates to multi-aperture magnetic core devices includingmeans and method for improving core transmitting characteristics.

With developments of multi-aperture cores for use in memory and logiccircuits have come numerous manufacturing problems. One of the moreimportant problems has been the identification of cores which result inunsatisfactory magnetic device performance due to poor transmittingcharacteristics. Strict control of manufacturing technique withattention to core material has not heretofore eliminated thedifiiculties and many core devices such as shift registers have beenassembled with apparently satisfactory cores, only to find malfunctionat some point of operation far short of the operating parametersdemanded by civilian and military specifications. The result of this isthat the general cost of core devices must support a substantialrejection rate, or alternatively, additional cores and windings must beemployed to accomplish flux clipping with the additional cost of laborand material incident to such practice.

Accordingly, it is one object of the present invention to provide amethod by which cores having ideal transmitting characteristics may beobtained.

It is a further object of invention to provide an improved magnetic coregeometry.

It is another object of invention to provide an improved magnetic coredevice capable of superior performance over a substantial range ofcurrent and temperature.

It is still another object of invention to provide a mag netic coredevice which avoids the need of intra-core flux clipping.

Other objects and attainments of the present invention will becomeapparent to those skilled in the art upon a reading of the followingdetailed description when taken in conjunction with the drawings inwhich there is shown and described an illustrative embodiment of theinvention; it is to be understood, however, that this embodiment is notintended to be exhaustive nor limiting of the invention but is given forpurposes of illustration in order that others skilled in the art mayfully understand the invention and the principles thereof and the mannerof applying it in practical use so that they may modify it in variousforms, each as may be best suited to the conditions of a particular use.

In the drawings:

FIGURE 1 is an enlarged view of a multi-aperture magnetic core includedto further explanation of the invention;

FIGURE 2 is a similar view of a magnetic core modified in accordancewith one embodiment of the invention;

FIGURE 2A is an elevation of the core of FIGURE 2;

FIGURE 3 is a similar view of a core modified in accordance with asecond embodiment of the invention; and

FIGURE 4 is a schematic diagram of a shift register circuit employingmulti-aperture cores modified in accordance with the embodiment ofFIGURE 3.

For a general description and definition of the material and energyrequirements of magnetic devices reference may be had to the papersMAD-Resistance Type Magnetic Shift Registers and Analysisof MAD-R ShiftRegisters and Devices by Dr. D. R. Bennion and Dr. David Nitzanrespectively, 1960 Proceedings-Special Technical Conference on NonlinearMagnetic and Magnetic Amplifiers, Philadelphia, October 26-28, 1960, pp.96 133, published by the A.I.E.E.

In US. Patent No. 2,995,731 to J. P. Sweeney there is shown a shiftregister comprised of multi-aperture ferrite cores linked by windingsand supplied by driving pulses in a manner to controllably shiftintelligence in the form of large and small pulses representative ofone-zero binary code. The manufacture of devices of this type presentlyrequires that the cores employed be subjected to tests which measurecore threshold and flux content and to a limited visual inspection.Notwithstanding such tests and notwithstanding an apparent compliancewith other core specifications, problems have been encountered whereinshift registers lose or gain information. Generally, shift registerswhich cannot transfer intelligence without significant alterationthroughout a range in temperature of between 50 C. and C. are notsuitable for military and certain commercial applications. A study ofrejected shift registers has revealed that in each case at least certainof the cores employed showed an excessive output voltage from thetransmitting aperture responsive to clearing or advance current when thecore was in a cleared state. Further tests have confirmed that shiftregisters composed of cores having a low voltage output operate properlythrough an acceptable range of temperature and current variations.

The result of the foregoing has been the development of the inventionwhich, as will be shown, calls for a core geometry substantiallydifferent from that urged by the prior art.

Referring now to FIGURE 1, a core 20 is shown, having a plurality ofminor apertures 24 disposed about a central major aperture 22 andincluding an input winding 21, an output winding 28 and a winding 26which may be considered as a clearing winding, similar in function tothe advance winding employed in Patent No. 2,995,731. Cores of this typeare comprised of die formed ferrite magnetic material having bistableproperties characterized by a hysteresis curve substantially but notexactly rectangular. In accordance with the accepted convention, thecore 20 may be considered as representing a zero when in its clear ornegative remanent state of saturation and as representing a one when inits set state with the core inner leg in the positive remanent state ofsaturation.

Such states are accomplished by the application of relatively small orrelatively large input pulses applied to an input winding such aswinding 21 which in the case of a zero input produces an insuflicient toalter the remanent state of the core and in the case of a one inputproduces an greater than the coercive force thereby reversing the senseof flux of the core inner leg. The application of a prime current to awinding (not shown in FIGURE 1) threading the transmitting apertureassures that the core, when set, will assume a flux configurationencircling the output winding. Intelligence transfer or interrogation isaccomplished thereafter by the application of a clearing pulse onwinding 26 having a magnetomotive force in a sense to drive the core inthe direction of negative saturation, producing a substantial fluxchange if the core is set and, in theory, only an elastic flux change ifthe core is clear. The output E on winding 28, is therefore proportionalto the amount of flux switched each time the core is cleared. With thewinding as shown in FIGURE 1, this flux will be the total switchableflux in the outer leg L4 and assuming a constant cross section, will beelastic flux. However, if the cross sectional area at the section C isnot the smallest cross section of the core, the flux in leg L4 willinclude remanent flux in addition to elastic flux. The effect of theadditional flux is that the output E, from a cleared core is larger thandesirable and such output may either appear to be a one or will causethe phenomenon of zero build-up. Evidence shows that a shift register ofthe type shown in FIGURE 4, including cores having excess material atthe transmitting aperture, will produce an erroneous one within severaladvance cycles.

The foregoing problems cannot be solved by exact die specificationsrequiring equal cross sectional area because of the existence ofmanufacturing tolerances. It will be readily appreciated that even inthe simplest multi-a-perture core geometry there will always exist anarea which is the smallest cross sectional area of a core. It will befurther appreciated that it is practically and economically impossibleto detect which particular combination of core dimensions produces thesmallest cross sectional area in each of the cores within a given coregeometry.

The solution of the foregoing problems as contemplated by the inventioninvolves a controlled constriction of the cross sectional area ofmulti-aperture cores whereby the transmitting aperture is made to have areduced cross sectional area. This may be accomplished in existing coresby removing core material from the L4 leg at the aperture selected to bethe transmitting aperture. New cores may be manufactured wherein thecore die produces a similar reduced cross sectional area at one of theminor apertures selected to be the transmitting aperture of the core. Ineither event, the reduction may be accomplished in a number of ways,including the removal of core material from any surface about the outeror L4 leg of the selected minor aperture. This practice has the effectof automatically assuring that the cross sectional area of the core issmallest at the transmitting aperture and therefore the remanent flux issubstantially zero and the total switchable flux at that point includesonly an elastic component thus making the zero output of a cleared coreas small as possible for a given core material.

The core geometry shown in FIGURE 1 is typical of a number of coregeometries manufactured under specifications calling for major and minoraperture dimensions and core material thickness and width dimensionswith each dimension including a plus or minus tolerance which may beconsidered for the purpose of discussion as :X mils. Taking this core asan example, it is first necessary to establish the general dimensions ofthe magnetic core material widths W and W/Z as shown in FIGURE 2. Thedimension T may be expected to vary from core to core within a givencore geometry by :X mils but due to the flatness or parallelism of theupper and lower surfaces may be carried Within a given core with aconsistency far greater than other dimensions. For this reason for allpractical purposes alteration of the W or W/2 dimensions will assurethat a selected cross sectional area may be made less than any othercross sectional area in the core. It is to be understood however, thatwhile this is preferred, reduction of the cross sectional area couldalso be accomplished by reducing the T dimension.

When dealing with modification to existing cores of a given coregeometry the W and W/2 measurements may be made on a relatively smallnumber of cores and a determination of the amount of core material to beremoved from the core may be accomplished and thereafter applied withoutfurther measurements to all of the cores of that core geometry.Considering the core of FIGURE 2, one aperture, such as aperture 36, maybe selected as the transmitting aperture of the core. Considering thedesign tolerance of the core to be iX mils, the removal of a portion ofmagnetic material, as indicated at 38, to the extent of twice thepermissible tolerance (2X mils J will assure that the cross sectionalarea through the section DD is not larger than any other cross sectionalarea through the core body or through other minor apertures of the core.This will in turn assure that the switchable flux about the aperture 38will not contain a significant remanen-t component and will thereforeproduce a low output voltage responsive to advance or clearing pulsesapplied to the core when in its cleared state as heretofore described.In the same manner, a reduction of the leg L4 by three times thetolerance (3X mils) will absolutely assure a minimum cross sectionalarea at the selected transmitting aperture 36. In core geometrieswherein the core material widths W are relatively small, it is preferredto remove only 2X mils from the leg L4 to avoid any possibility ofadversely affecting the core threshold. In most applications wherein thecore material widths W are relatively large, a reduction by 3X mils isacceptable. It should be kept in mind, however, that the theoreticallypreferred Width dimension of a transmitting aperture should be equal toall other similar dimensions and that the invention contemplates makingthe dimension as close to equal as possible but in any event not largerthan any other cross sectional Width.

Removal of core material may be accomplished in any desired manner as byfiling, sanding or other abrasive techniques. The removal, as indicatedby the slot 38 as shown in FIGURE 2 and 2A, may also be accomplished onthe top or bottom surfaces of the core or-may be accomplished byenlarging or removing material from the L4 portion of the apertureselected to be the transmitting aperture. Following removal of corematerial the constricted aperture may be marked for identification as anaid in assembly of magnetic devices using altered cores.

The :foregoing technique of selecting an aperture and removing materialfrom the leg L4 thereof may also be applied to core dies so that coresmay be manufactured having a constricted cross sectional area at aselected minor aperture. The preferred way of accomplishing crosssectional area constriction in new cores is by enlarging the diameter ofthe minor aperture chosen to be the transmitting aperture. In FIGURE 3,the aperture 34 is enlarged by an amount sufficient to assure the crosssectional width along the section E--E is as small as any cross sectionin the core. For example, assuming that the die specifications normallyrequire that the apertures A1, A2, A3 and 34 to be equal to 30 mils witha tolerance of 1-1 mil, a new die made in accordance with the inventionwould include apertures A1, A2 and A3 of 30 mils with aperture 34 being32 milsimil. In this manner, and variation of one mil in any of theapertures A1, A2 or A3 and 34 will leave the aperture 34 at least aslarge and the cross sectional area thereat least as small as anyremaining cross section of the core. Care must be exercised to assurethat the reduction of magnetic material does not reduce the corematerial linked by the output winding to a point wherein an insuflicientflux will be present in the leg L4 to provide proper gain. By basing theamount of constriction on the manufacturing tolerance of core this maybe avoided.

In FIGURE 4, there is shown a shift register circuit of a well knowntype, wherein odd, 0 and even E" cores are arranged to be driven bypulses applied to ad- Vance windings 48 and 52 and by prime current viawinding 58. Each of the cores OE include a major aperture 45 and aplurality of minor apertures 46, as in the cores above described.Intelligence is fed into the register by pulses applied to the inputWinding 44 and is transmitted from core to core by advance pulsesalternately applied to windings 48 and 52. The constant application ofprime current via winding 58 assures that if a core is in its set statethe core magnetization will be properly altered to assure coupling ofthe windings 43 prior to the application of advance current. It is oftranscending importance that the intelligence shifted into a registernot be lost during successive advance cycles and, moreover, that falseintelligence due to zero build-up not occur. In accordance with theinvention, each of the O and E cores of the register includetransmitting apertures, such as 42, which are enlarged relative to theother minor apertures of the core as heretofore described so as toinsure that the cross sectional area of core material at suchtransmitting aperture is equal to or smaller than any other crosssectional area of the core. In this manner, the application of advancecurrent to a core in its cleared state will not produce output voltageson coupling windings 43 of a value sufficient to either set a succeedingcore or to cause the additive effect of zero build-up whereby a falseone will be produced at the output winding 49. Loss of ones will beavoided by assuring that the diameter of the transmitting aperture 42 islimited to a deviation of no more than several tolerances of theremaining apertures.

The shift register of FIGURE 4 is exemplary of magnetic devices of thetype wherein the present invention can be used to substantial advantage.In any magnetic device having one or more multi-aperture cores coupledto an additional core or cores by coupling windings similar to thewinding 43, as shown in FIGURE 4, the output voltage responsive todriving a cleared core may be minimized by the application of theinvention.

In a core of the configuration of FIGURE 2 comprised of a magneticferrite material uanufactured by the General Ceramics Company ofKeasbey, New Jersey and identified as No. 5209 material, the followingwas observed. The core included dimensions of T :39 mils, W=40 mils, andW/2=20 mils, :1 mil. Removal of approximately 3 mils from the leg L4, asindicated by 38 in FIGURE 2, reduced the output voltage E of the core inits cleared state from 230 millivolts to 60 millivolts.

In a shift register of the type shown in FIGURE 4, the use of coreshaving 5% reduction of the L4 dimension of the transmitting apertureproduced a range of satisfactory operation as measured by advancecurrent vs. prime current improved by 25 percent.

Changes in construction will occur to those skilled in the art andvarious apparently diiferent modifications and embodiments may be madewithout departing from the scope of the invention. The matter set forthin the foregoing description and accompanying drawings is offered by wayof illustration only. The actual scope of the invention is intended tobe defined in the following claims when viewed in their properperspective against the prior art.

I claim:

1. The method of improving the transmitting characteristics of magneticcores of the type having a major aperture and a plurality of minorapertures defining inner and outer legs of magnetic material includingthe steps of ascertaining the cross sectional area of the core body asmeasured from the said major aperture to the outer pen'phery of the coreto a given tolerance, selecting one of said minor apertures as atransmitting aperture, reducing the cross sectional area of the saidcore by removing magnetic material from the outer leg of the selectedaperture to an extent of twice the tolerance as ascerained whereby thecross sectional area of the core through the selected aperture is equalto or less than other cross sectional areas of the core.

2. In a method of improving the binary one and zero transmittingcharacteristics of magnetic cores of the type having a major apertureand a plurality of minor apertures defining inner and outer legs ofmagnetic material including the steps of ascertaining the manufacturing6 v tolerance of the cross-sectional area of material of the core body,as measured from the major aperture to the periphery of the core,selecting one minor aperture as a transmitter aperture for said core,dimensioning the core so that the said cross-sectional area of materialat points about said major aperture in the absence of a minor apertureand the sum of cross-sectional .areas of the inner and outer legs of theminor apertures other than at the said one minor aperture areapproximately equal, dimensioning the inner and outer legs of materialat said one minor transmitter aperture so that the sum ofcross-sectional areas of material of said legs is equal to the saidcross-sectional area at other points about said major aperture less anamount equal to twice the said tolerance as ascertained.

3. The method of claim 2 including the step of marking the said oneselected minor aperture selected as a transmitter aperture for said corefor identification as an aid in assembly of magnetic devices using saidcore.

4. In a method of improving the binary one and zero transmittingcharacteristics of magnetic cores of the type having a major apertureand a plurality of minor apertures defining inner and outer legs ofmagnetic material including the steps of ascertaining the manufacturingtolerance of the cross-sectional area of material of the core body, asmeasured from the major aperture to the periphery of the core, selectingone minor aperture as a transmitter aperture for said core, dimensioningthe core so that the said cross-sectional area of material at pointsabout said major aperture in the absence of a minor aperture and the sumof cross-sectional areas of the inner and outer legs of the minorapertures other than at the said one minor aperture are approximatelyequal, dimensioning the inner and outer legs of material at said oneminor transmitter aperture so that the sum of crosssectional areas ofmaterial of said legs is equal to the said cross-sectional area at otherpoints about said major aperture less an amount equal to three times thesaid tolerance as ascertained.

5. The method of claim 4 including the step of marking the said oneselected minor aperture selected as a transmitter aperture for said:core identification as an aid in assembly of magnetic devices usingsaid core.

6. In a device for transferring binary one and zero information acircuit including a plurality of multiaperture cores formed of magneticmaterial having square loop characteristics, input means to supply saidcores with information signals, output means driven by said cores tooutput information and coupling means coupling said cores fortransferring information therebetween, drive means linking said cores toswitch flux therein to effect transfer of information, each said coreincluding a major aperture and a plurality of minor apertures positionedin said body to define inner and outer legs of material at each minoraperture, the sum of cross-sectional areas of material of said inner andouter legs of material at one of said minor apertures being less thanthe sum of crosssectional areas of material of the inner and outer legsof material at all of the other said minor apertures and the sum of saidcross-sectional area of said inner and outer 'legs of material at saidother minor apertures being approximately equal to or greater than thecross-sectional area of the square loop material surrounding the saidmajor aperture at points apart from said minor apertures, the said oneminor aperture having the least cross-sectional area of magneticmaterial being the transmitter aperture for the said core whereby tominimize zero level transfer from each of said cores.

7. The device of claim 6 wherein the said coupling loops link thetransmitter aperture of a given core to one of the other said minorapertures of an adjacent core whereby to minimize zero level transmittedfrom a given core and to further minimize zero level input to theadjacent core.

8. The device of claim 6 wherein the said drive means 7 includes a firstdrive Winding threading said cores to switch flux about said majorapertures and a second drive winding threading the core transmitterapertures to switch flux locally thereabout to prime said cores fortransfer.

References Cited by the Examiner UNITED STATES PATENTS 2,799,822 7/1957Dewitz 340-174 2,907,991 10/1959 Van Allen 340174 8 Briggs 340-174Kelley 340-174 Bullock 340174 Richard 340174 Mathers 340'174 Bennion340-174 BERNARD KONICK, Primary Examiner. IRVING SRAGOW, Examiner. M. S.GI'ITES, R. J. MCCLOSKEY, Assistant Examiners.

2. IN A METHOD OF IMPROVING THE BINARY ONE AND ZERO TRANSMITTINGCHARACTERISTICS OF MAGNETIC CORES OF THE TYPE HAVING A MAJOR APERTUREAND A PLURALITY OF MINOR APERTURES DEFINING INNER AND OUTER LEGS OFMAGNETIC MATERIAL INCLUDING THE STEPS OF ASCERTAINING THE MANUFACTURINGTOLERANCE OF THE CROSS-SECTIONAL AREA OF MATERIAL OF THE CORE BODY, ASMEASURED FROM THE MAJOR APERTURE TO THE PERIPHERY OF THE CORE, SELECTINGONE MINOR APERTURE AS A TRANSMITTER APERTURE FOR SAID CORE, DIMENSIONINGTHE CORE SO THAT THE SAID CROSS-SECTIONAL AREA OF MATERIAL AT POINTSABOUT SAID MAJOR APERTURE IN THE ABSENCE OF A MINOR APERTURE AND THE SUMOF CROSS-SECTIONAL AREAS OF THE INNER AND OUTER LEGS OF THE MINORAPERTURES OTHER THAN AT THE SAID ONE MINOR APERTURE ARE APPROXIMATELYEQUAL, DIMENSIONING THE INNER AND OUTER LEGS OF MATERIAL AT SAID ONEMINOR TRANSMITTER APERTURE SO THAT THE SUM OF CROSS-SECTIONAL AREAS OFMATERIAL OF SAID LEGS IS EQUAL TO THE SAID CROSS-SECTIONAL AREA AT OTHERPOINTS ABOUT SAID MAJOR APERTURE LESS AN AMOUNT EQUAL TO TWICE THE SAIDTOLERANCE AS ASCERTAINED.